<sls5448@[EMAIL PROTECTED]
> wrote in message
news:72b67ec4-584d-4e42-80e9-18c60e6e67a7@[EMAIL PROTECTED]
Apr 14, 12:13 pm, "Mike" <m...@[EMAIL PROTECTED]
> wrote:
> <sls5...@[EMAIL PROTECTED]
> wrote in message
>
> news:2a905b5d-e2ab-4848-bd6a-4c2f4d0962c7@[EMAIL PROTECTED]
>
>
>
>
>
> >I have a 93 grand cherokee with 200Kmiles. It idles smoothly and runs
> > ok but I cannot hold a steady rpm over 1000 RPM.It surges slightly
> > over a 300 RPM range. I've replaced cap, rotor, wires, coil, and
> > plugs. I've checked all the vac*** hoses for leaks. I even went as far
> > as to plug all the vacuun ****ts in the manifold and throttle body. It
> > still surged slightly.
> > I removed the throttle body and cleaned it thoroughly, replaced the
> > TBI gasket. I've used seafoam in the gas tank (it ran really crappy
> > until I filled up again). Cylinder compression is good considering
> > it's age (around 150psi max, 130 min).
>
> > Fuel economy is less then I expect. In a relatively hilly area I get
> > around 11MPG in mixed (mostly city) driving. Overall drievability is
> > pretty good and power is good all the way to redline. This leads me to
> > believe I have enough fuel pressure.
>
> > Any ideas?
>
> > Thanks in advance!
>
> > sls
>
> Surging is usually a sign of running lean. I would check the operation
of
> the O2 sensor(s) with a scan tool to make sure they are working
properly. To
> do so you would need a scan tool that is capble of reading sensor
values.
> You
> can also check O2 performance with a multimeter. It may be cheaper just
to
> replace the O2 sensors from the start due to the high mileage on the
> vehicle.
>
> I would check the fuel pressure as well just to rule that out as a
> possibility. The fuel pressure regulator increases fuel pressure under
power
> conditions so it could still be low at cruise.
>
> What engine do you have ? If you have a V8 they have a pan on the bottom
of
> the intake that is prone to leaking, the only way to check it is to
remove
> the
> intake.
>
> Also check your EGR valve for proper operation. If it opens too far or
at
> the wrong time that may cause a surge also.- Hide quoted text -
>
> - Show quoted text -
Thanks for the suggestions. Is it possible the O2 sensor or EGR could
be bad and not throw a code? So far I don't have any codes from the
ECU.
Yes, especially a failing O2 sensor. The O2 sensor will be at the
extreme
end of it's range which is still within specs.
It is a V8. I'll save pulling the intake as a last resort. Is there a
method for a shadetree mechanic like me to test fuel injectors?
If you wanted to remove the fuel rail and rig up a way to actuate the
injectors you could check the spray pattern.
Thanks again!
sls
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